Some investigation reports that the necessity of measuring a condition of a driver, since automobile incidents are mostly caused by a human factor.
For example, automobile incidents due to an inattentive or napping long-distance truck driver attract some social attention. Automobile incidents due to an abnormality of cardiovascular system also attract social attention. Especially, in the aging society, the abnormalities of the cardiovascular system may attract greater social attention.
For such reasons, the following patent documents 1 and 2 disclose a method of monitoring whether a driver is in a normal condition or an abnormal condition by measuring a heart rate in a vehicle. Those technologies determine whether it is in a normal or an abnormal based on a determination of whether a monitoring value is out of a threshold value or not. In one case, the monitoring value is a high frequency component HF of a heart rate or a heartbeat interval variation HRV. The threshold value is a predetermined value which can be compared with an absolute value of the high frequency component HF. In another case, the monitoring value is an increasing/decreasing rate of the high frequency component HF from an initial stage or an increasing/decreasing rate of the high frequency component HF within a predetermined time period. The threshold value is a predetermined value which can be compared with the increasing/decreasing rates.
The patent document 3 discloses a processing method of electrocardiograph waveform.
The patent document 4 discloses a technology for estimating a heartbeat interval from a heart pulse signal.
Patent Documents
1: US Application Publication 2008/0071177 (WO2005/112764)
2: JPH11-195198A
3: JP2007-301101A
4: JP3729143B